The invention relates to a low-pressure sodium vapor discharge lamp provided with a discharge tube which is equipped with at least two internal electrodes, each of the two electrodes being connected to at least one lead-through conductor through the wall of the discharge tube, with the lead-through conductor enveloped both at the area of the wall of the discharge tube and inside the discharge tube by a protective layer consisting of glass.
A known low-pressure sodium vapor discharge lamp of the aforementioned kind is described, for example, in U.S. Pat. No. 3,519,865. In this known lamp, the protective layer has a substantially uniform thickness and an additional auxiliary means, such as, for example, a screening disk, is present between the electrode and the protective layer. The additional auxiliary means serves to prevent the protective layer being reached by a sodium--present in the discharge tube--and attacked by it. The complication of such an additional means in the discharge tube is a disadvantage.